Raw material used for producing heat-resistant resins, heat-resi

Details Raw material used for producing heat-resistant resins, heat-resi Raw material used for producing heat-resistant resins, heat-resi

1997-05-20

1999-12-07

Smith, Jeffrey T.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

5263182, C08F22606, C08F22204

Patent

active

059985569

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a raw material used for producing heat-resistant resins, heat-resistant resins which are produced from the raw material and have excellent heat resistance, fine appearance and a low coloring factor, and a process for producing the heat-resistant resins.


BACKGROUND ART

Methacrylic resins made from methyl methacrylate as a principal component have excellent weatherproof and optical properties, and relatively balanced mechanical, thermal and fabrication properties. The methacrylic resins are used in various fields, such as automobile parts, electrical equipment parts, face plates, signs, covers for lights, ornaments, and variety goods, because of their properties mentioned above.
However, the methacrylic resins are insufficient in terms of heat resistance, and therefore their use in the fields requiring shape stability at high temperatures is limited. Thus, there is a strong demand for an improvement of the heat resistance of the methacrylic resins.
Many methods have been proposed for improving the heat resistance of the methacrylic resins. Examples of the proposed methods include the copolymerization of methyl methacrylate and N-aryl maleimide (Japanese Publication for Examined Patent Application, No. 9753/1968), and blending the copolymer of methyl methacrylate, .alpha.-methyl styrene and maleic anhydride with a methyl methacrylate copolymer (Japanese Publication for Unexamined Patent Application, No. 122536/1984).
Moreover, as known methods for producing transparent methacrylic resins of improved heat resistance and reduced coloring factor, there are methods including copolymerizing methyl methacrylate and N-cyclohexylmaleimide within a specific range (Japanese Publication for Unexamined Patent Application, No. 156115/1987 and 177009/1987), and a method including copolymerizing methyl methacrylate and N-cyclohexyl maleimide and then reducing raw material monomers remaining in the resultant copolymer (Japanese Publication for Unexamined Patent Application, No. 112612/1987).
By copolymerizing a methacrylic ester such as methyl methacrylate and N-substituted maleimide such as N-cyclohexylmaleimide, it is possible to achieve some improvements in respect of the heat resistance, transparency, and coloring factor, thereby providing a transparent heat-resistant resin for optical uses.
However, in such a heat-resistant resin, the improvement of the heat resistance depends on the amount of N-substituted maleimide. Therefore, in order to obtain a heat-resistant resin of improved heat-resistance, it is necessary to increase the N-substituted maleimide unit in the heat-resistant resin. However, the increase of the N-substituted maleimide unit causes a problem that the resultant heat-resistant resin tends to color (yellow).
In the case of N-substituted maleimide-based heat-resistant resins produced from N-substituted maleimide as one of the raw materials, the coloration of resin products is generally known. However, some uses of the resin products strongly require a reduction in the coloration of the resin products. Thus, there has been a demand for the development of N-substituted maleimide-based heat-resistant resins of reduced coloration (referred to as "low coloring factor" in the present invention).
In the production of molded articles by molding the heat-resistant resins obtained by the above-mentioned methods, the molded articles sometimes had lowered surface smoothness, and showed deterioration in their optical properties including transparency, and appearance.
The present inventor studied to find the cause of the lowering of the smoothness, and discovered that non-polymerizable impurities derived from the raw material in producing the N-substituted maleimide were the causes of such a lowering of the smoothness.
Since most of such impurities have their melting points at temperatures lower than 200.degree. C., when a heat-resistant resin containing the impurities is molded, the impurities volatilize due to heat in molding, and adhere to the mold surfaces. As a

REFERENCES:
patent: 5073615 (1991-12-01), Shen
patent: 5319043 (1994-06-01), Shen
patent: 5328962 (1994-07-01), Shen
patent: 5556991 (1996-09-01), Kita et al.

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